Effect of loading density of sockeye salmon, Oncorhynchus nerka (Walbaum), eggs in incubation boxes on mortality caused by infectious haematopoietic necrosis

Infectious haematopoietic necrosis (IHN) can cause massive mortalities of sockeye salmon, Oncorhynchus nerka (Walbaum), cultured in hatcheries. One method of enhancing sockeye salmon populations is to use a streamside egg incubation box from which the fry are automatically released into the stream as they emerge from the gravel. In this system, however, IHN epizootics occur as the fry emerge and continue for up to two months after the fry leave the box (Mulcahy, unpublished data). In as much as the high density of eggs and alevins in incubation boxes might be conducive to the fulmination of an IHN epizootic, we varied the egg density in incubation boxes and studied the cffect on mortality caused by IHN.